function R = square_pump(obj, amp,freq, offset)
%SQUARE_PUMP Summary of this function goes here
%   Detailed explanation goes here
    switch obj.sol_opt
        case 'periodic'
            R = chebfun({   0,           amp,          0        }, ...
                        [0    0.25/freq      0.75/freq   1/freq]) + offset;
        case 'transient'
            error('square_pump is only valid in the "periodic" mode.');
    end
end

